This invention relates generally to the field of propane delivery systems, where liquid propane is stored under pressure in a tank and the propane is delivered as a gas through supply conduits to devices which utilize the propane gas as a fuel. More particularly, the invention relates to such systems where a pair of regulators are provided in the gas supply conduits, the first regulator reducing the pressure in the supply conduit to approximately 10 psi and the second reducing the pressure to less than 0.5 ounces per square inch for use by household appliances and the like. Even more particularly, the invention relates to such systems where a secondary containment tank, of relatively small volume, is provided in the supply conduit between the two regulators, the secondary tank retaining any liquid propane which has condensed in the supply conduit and having a float valve to prevent liquid propane from flowing through the second regulator and to the household devices.
The use of propane gas to provide fuel for various devices or household appliances is well known. In the typical systems, a large tank capable of holding hundreds of gallons of liquid propane is provided at an external location. The tank is filled with liquid propane under pressure ranging from about 10 to 125 psi, the actual pressure being dependent on the ambient temperature, the low value occurring when the outside temperature is below zero degrees and the upper value occurring when the temperature is in the eighties or higher. A portion of the liquid propane changes to propane gas and is passed through a first regulator which reduces the pressure to about 10 psi. The propane gas is then conducted through a supply conduit or pipeline to a second regulator, which reduces the pressure of the gas in the supply conduit to less than about 0.5 ounces per square inch, which is a desirable pressure for use in most appliances and devices.
The tank is kept external to and separated a distance from the building for safety reasons. This means that the supply conduit must be relatively lengthy and is exposed to the elements to some degree. When the ambient temperature drops, the propane gas in the supply conduit may condense into liquid propane. Likewise, if the main tank is overfilled, liquid propane may be forced into the supply conduit. In either case, it is possible for liquid propane to pass through the supply conduit and into the household appliances or other devices. This is very dangerous, as the liquid propane may blow out the seals and a fire or explosion may result.
It is an object of this invention to provide a system for the delivery of propane gas, or any other similar gas where condensation back into the liquid phase in the supply conduit is detrimental, which incorporates a secondary containment tank to receive and retain any liquid propane which has condensed or been inadvertently drawn into the supply conduit, where the liquid propane is allowed to vaporize in the tank for passage through the second regulator. It is a further object to provide such secondary tank with a valve means which shuts off all flow from the secondary tank in the event the liquid propane level nears the point where it would be drawn into the second regulator.